Thickener



Sept 28,192111vv y F. G. LEsNiAK' y --2,450,006

THICKENER Filed Aug. 14, 1943 ATTORNEY i lNvsm'ozL 7 "FRANK G- LESNIAK Patented Sept. 28, 1948 THICKENER Frank G. Lesniak', Laurel, Miss., assignor to Masonite Corporation, Laurel, Miss., a corporation oi Delaware Application August 14, 1943, Serial No. 498,907 2 Claims. (Cl. 210-'V-149) vThe present invention relates to apparatus for fiber board and paper manufacturing, and especially toa thickener to materially reduce the amount of water in watery fibrous stock. It relates more specifically to a thlckener which is so constructed that with use of a given screen area more water can be removed from the stock material than has heretofore been removed by use of thickeners previously known.

Conventional thickeners previously used consisted of a plane screen set at a slant between two spaced apart troughs positioned at different elevations. Stock consisting of high water content. e. g.. approximately 99% water and 1% fiber'. was fed to the top portion of the screen, and the watery fibrous stock moved rapidly over the surface of the screen to the lowest portion thereof. In passing over the screen surface some of the water passed through the screen, and the fibrous stock and the remainder of the water flowed over the screen surface into the stock removal trough positioned adjacent the lowest portion Aof the screen.

In practice, difficulties have been encountered in using the previously known thickeners described above. With a steep slant, the watery bcr stock moved so rapidly over the screen surl, face that in a given distance only a smallproportion of the water passed through the screen surface. With too little slant the stock tended to move slowly and pile up. To remove the proper proportion of water in order to obtain the proper consistency in the dewatered stock, either the screen area had to be increased or .the stock had to be passed over a second, and sometimes a third, thickening apparatus.

It is therefore an object ofthe present invention to provide a thickener which is adapted to remove the optimum proportion of water with use of substantially minimum area of screen surface. For example, the invention may be put to use for so thickening fibrous stock, which has been refined and then diluted to the extent adapted-for screening out oversize fiber bundles and the like, that it will have the proper consistency to be efciently formed into sheet form on a Fourdrinier or other forming machine.- If the stock to be formed on the Fourdrinier wire has too much water, dlfllculty is encountered in making a satisfactory wetlap for ber board manufacture or web for paper making.

Another object is to provide a thickener over which the watery brous stock will move by its own inertia in a relatively horizontal plane in the region where the fiber stock nows onto the screen surface and in an increasingly vertical plane or slant as the liber stock moves over the screen surface toward the bottom thereof.

An additional object. is to provide a thickener which has a relatively convex curved screen surface extending between an elevated supply trough or other supply means and a stock removal trough located at a lower level.

A practical embodiment of the invention is rep-k resented in the accompanying drawing forming a part of this specification, and showing the improved screen of the present invention interposed between an elevated stock supply-trough and a stock removal trough located in front of the supply trough and at a lower level, said screen presenting a convex upper surface andwith its upper portion upon which the stock is supplied substantially horizontal, and with said screen being of increasing slant towards the discharge trough.

In said drawingFig. 1 is a part-sectional isometric view of the improved thickener, showing the screen surface partly broken away; and

Fig. 2 is a transverse sectional view.

Reference character Ill designates a thickener apparatus with side walls I2 and I4 so positioned in relation to the base of thel thickener as to form the water-exit trough I6. Posts I8 serve to support a screen structure positioned above trough I6.

The stock is supplied to' the thickener l0 by supply trough 20, from which it ows through passages 22 into the now-smoothing or `equalzing trough 2l, and from trough 24 flows through passages 26 (which may be provided with bafflesnot shownto further equalize the flow), said passages 28 leading to screen 28. Thescreen 28 is positioned in front of trough 24, and the passages 26 are so positioned as to permit flow of stock material from trough 24 onto the screen surface.

Screen 28 is substantially convex in shape, being here shown as substantially part-circular in section, and ls fixed and supported on trusses 30 and 32. If desired a coarser screen 34 may be placed beneath the screen 28 in order to additionally support said screen 28 throughout its area. The screen structure is so positioned with relation to the supply trough 24 that the stock is supplied upon a region of screen area which is substantially horizontal, and then passes over a .screen surface inclined downwardly and forwardly to allow stock material to readily flow from the top of the screen to the bottom thereof.

At the bottom of the screen structure, a stock yremoval trough 38 is formed between the walls 3` i4 and I8. and said trough il is so positioned with relation to the bottom of the screen as to receive the fibrous stock and retain water flowing over thel surface oi the screen. 'Ihe troughs and screen are closed in by end walls. one of which is represented by reference character 4l.

In operation. watery fibrous stock of approximately 1% of fiber content or less. for example. is flowed into the back supply trough Il as indicated by the direction arrow A. The stock material flows through the passages 22 into the front trough 24 as indicated by the direction arrow B. It is preferable in operation to have back and front delivery or supply troughs 2l. 24 in order to smooth out the flow of water so that a relatively smooth stream will flow upon the screen surface. The stock material flows from the front trough It through the passages 28 onto the screen surface 28, the water which passes thorugh the screen being removed by trough Il.

The screen surface 23 is substantially convex in contour, and the stock material flowing through the openings 26 will at first-move relatively slowface is relatively'horizontal. At this point the stock is quite liquid, and since the stock moves relatively slowly at this point, water will pass freely through the screen 2l into the water removal trough I6, as indicated by the vertical spaced arrows on Fig. 2. As the fiber stock moves down over the screensurface, the angle of the screen becomes increasingly greater, that is, the

slant of the screen increases as the screen extends away from the supply trough, and even though some water has been removed from the stock. the

.rate of now of the stock will not be materially decreased.

As the water content of the liber stock vis decreased, the angle of inclination of the screen is increased. As a result of the increased angle on which the thickened stock moves, there will .be no tendency tor jamming up of the stock near the bottom portion of the screen. The thickened fiber stock ows into trough it, and leaves the thickener as indicated by the arrow C. The water which passes throughthe screen flows out through trough IB as indicated by arrow D.

The main screen 28 is ofl relatively fine mesh, and in practice screens of 60 to 'l0-mesh are satisfactory although considerable variation in this respect is possible. In the drawing a supporting or reinforcing screen Il is shown, and this screen may be quite course, as for example, about 14- mesh.

The fiber content o! stock coming from the stock trough at the bottom' portion of the screen is materially increased. as for example this stock may have a consistency of about 2 to 3% fiber and with the remainder water.

I The thickener apparatus described herein :is simple in construction and is very effective in increasing the volume of stock which may be dewatered to the proper consistency as compared to 1thev previously used thickeners provided with screens of the simple inclined plane type. It has been found `that through the use o! the convex l screen structure the capacity of the screen inde- `1y because the upper portion of the screen sur- Number Name Date 495.260 McEwan Apr. 11, 1893 628,311 Goodfellow July 4, 1899 1,195,875 Toh-ms Aug.' 22, 1916 1,480,500 Brown ----.f Jan. 9, 1924 1,544,904! Herb 1 July '7. 1925 FOREIGN PATENTS Number Country, Date 42,134 Norway Nov. 9, 1925 48.305 Netherlands ..--...-s- Aug. 15. 1939 watering stock to the proper consistency has been increased approximately 50 to 100% as compared to a straight screen slanting in a single plane directly through the same distance from supply trough' to stock removal trough.

The apparatus shown and described illustrates a preferred embodiment of my invention, but which may be modified to accomplish equally satistactory results. It is to be understood that such modifications fall within the spirit and scope of the present invention and that the invention shall only be limited by the breadth of the appended claims.

I claim:

1. Apparatus for reducing the water content of watery fibrous stock. which comprises the combination of a supply means for the stock. removal means for removing stock with reduced water content at a level lower than the level of the supply means, and a iixed convex screen in front of the supply means and inclined forwardly and downwardly therefrom to the removal means, the

contour of the screen beingsuch as to cause the stock to move over the surface of the screen -by its own inertia toward the stock removal means, nrst moving relatively slowly over a relatively horizontal screen area near the upper part of .the screen when containing the highest percent-` age o! water, and then moving with increased speed over a more inclined screen area as it approaches the stock removal means when containing a reduced portion of water, whereby to cause water to separate from the stock and pass through the screen, and to avoid, through the increased speed attained, the jamming upV ofA the stock near the bottom of the screen.

2. Apparatus for reducing the water content of watery brous stock, which comprises the combination of e. stock supply means, stockjremoval means spaced from the supply meansfancl positioned at a level lowerthan the level of the supply means, and a iixed convex screen, mounted on stationary supports, extending from the supply means to the removal means. said screen presenting a relatively horizontal surface portion adjacent to the supply means and a surface portion of increased slant adjacent to the removal means.

FRANK G. LESN'IAK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS` 

